Antenna support



Nov. 15, 1960 H. J. FRY

ANTENNA SUPPORT Filed Feb. 10, 1958 fig I 1N VENTOR ATTORNEY i at2,960,693 Patented Nov. 15, 1960 ANTENNA SUPPORT Henry '1. Fry,Arlington, Va., assignor to Melpar, Inc., Falls Church, Va.,a'corporation-o'f New York Filed-Feb. 10, 1958, Ser. No. 714,237

4 Claims. (Cl. .343-765) mounted rearwardly thereof The disadvantage ofthis type of support, that is, having the pivot point behind theantenna, is that 'it requires a very heavy structure "behind thereflector-in order to maintain'the proper surface o'f'the reflector.Also,'the warping effect on-the re- 'flector caused by the antenna feedadds to the requirementof a heavy structurebehind the reflector.

The present invention overcomes this objection-in the preferred form byproviding 'asupporting means between the reflector and the antenna feed.This supporting means is located at or near the center of gravity of theantenna device and the pivot-pointis thus placed on the supportingmeans. The reflector and the antenna feed are attached to an oval-shapedmember by tubular rod members. The oval-shaped member is movably mounted-on a yoke member which has drive means attahedthereto and therefor.

-Further, this invention is also concerned with 'an antennadevice thatminimizes-the effectivenessofjjamming long-range radar systems. At thepresent time, many radar installations produce noinformation at allregarding theazimuth position of an incoming aircraftbecause thejammingequipment onzthe aircraft is capable-of producing a signal on theradar lindicator no matter what the radar antenna bearing position mightbe. This occurs because the high powerpresently available to jammers isreceived on the antenna sidelobes although'the-side lobe gain might besome 20 db or more below the' basicantenna gain.

The obvious solution to this jamming problem involves a reduction in theantenna side lobe level. Many 'difierent attemptsat side lobe reductionhave been-undertaken during the past years. The results of the majofityof these attempts indicate only marginal success. -In general, theseradar systems were all concerned'with reductions in the close-in sidelobes which are caused by diflraction phenomena. These side lobesare-normally associated with the edge eflects of the'reflector or lensforming the antenna and, consequently, cannot be eliminated andonly-with great difiiculty can bereducedbelow 30 db.

Theside lobe problem associated with minimizing the effect of anairborne jamrner is considerably diiterent from that of minimizingclose-in lobes. This problem involves levels of the order-of 50 db down;the side lobe reduction is not required in regions close to "the mainbeam but, rather, in regions away from the beam. These lobes arenormally associated not with diffraction but, rather, with scattering ofenergy fromthe reflector edges and from the feed assembly. It ispossible to minimize this scattered energy by obtaining side lobesof-the order of 50 db. This type of side lobe reduction is carried outby encasing the antenna in'a tunnel-like structure which surrounds'thereflector 'and effectively capturesthe scattered energy. One end of thetunnel is fastened to the reflector, while the other end serves as'theantenna aperture.

An object of the present invention is the provision of a movably mountedantenna device Which may be tilted during rotation by power means.

Another object is rto'provide an adjustable construction of the-antennadevice mounting whereby it may bemoved to any azimuth settingup to thefull 360, and raised to any desired angle of 'elevation.

A further object of the invention is the provision'of a movably mountedradar antenna device having a side 'lobereduction tunnel for minimizingthe effectiveness of jamming a radar system.

Still another object is to provide a considerablylighter antenna devicethat can be constructed so that the reflector surface has a minimum ofexternal forces tending to warp it and consequently requires a minimumof structural parts.

An additionalobject is-the provision of-an antenna reflector which needsonly 'a surface capable of supporting its own weight and'shapesubstantially at the 'center of gravity of the antenna device.

These and other objects of the present invention are realized by theprovision of supporting a movably mounted oval-shaped member on avertical rotatable yoke substantially at the-centero'fgravity of theantenna device. The oval-shaped member further supports a paraboloidalreflector and'an antenna feedassem'bly :by means of rod members and thelike which are attached to the ovaltration only, and not as alimitationupon .the scope of the'invention, which is defined in theappended claims.

In the drawings: Figure 1 is a perspective view of'the preferredembodiment of the present invention'applieditothereflector of a searchradar installation;

Figure 2 is a sideview of Figure -l; and Figure 3 is za mo'dified formof thepresent invention using a tunnel'structure.

'In accordance withone embodiment of the invention,

as illustrated rinFigures '1 and 2, the antenna device which isindicated "by reference numeral 10, has a-stationary base plate '12 upon.WhiCh the antenna device 10 is placed thereon. rAacasing 14 is mountedon the .base 12 forhousingtherotatingmeans which is comprised of agearing-assembly :16 anda-motor 18. .A yoke '20.-has

uprightly outwardly curved bar portions 22, 2'4 and a "vertical shaftportion 26'which is rigidly connected downwardly to the midwayjunetional point of the bar portions :22, 24. The .vertical shaft .26 isrotated by the driven gearing assembly 16.

'An' oval-s'haped member 28 is pivotably .mounted on theuppermost-ends-of the bar portions 22, 24. The oval-shaped member 28iscurved with the exception of a flat bottom ,portion 30, the purpose ofwhich will more fully appear hereinafter. A platform 32 is located atone of the uppermost ends of the bar portion 24 and has mounted thereonagearing assemble 34-and a motor 36. This driving mechanism 34, 36engages the substantially vertically disposed, metallic oval-like member28 which is supported in spaced relation from a paraboloidalreflector 38by a plurality of radially spacedapart tubular rod members 40. The rodmembers shown "on the lower side thereof are angular-1y disposedrelative to the horizontal to contact the flat bottom portion 30 of theoval-shaped member 28. The reflector 38 is fed by a horizontallypolarized electromagnetic wave through a wave guide 42 and a feeder 44from a transmitter (not shown). The feeder 44 is rigidly connected tothe oval-shaped member 28 by the wave guide 42 and by a pair of tubularrod members 46. The entire feeding means is positioned below thehorizontal scanning plane and the reflector axis. The energy isreflected in a predetermined pattern which is controlled by theconfiguration and size of the reflector 38.

Referring to the two arrows in Fig. 1, it is readily seen that theantenna device may be continuously rotated by the driving mechanism 16,18 in azimuth and selectively tilted by another driving mechanism 34, 36during rotation to any desired angle of elevation. Further, the yokesupporting means 20 is located at or near the center of gravity of theantenna device which gives a more reliable, rigid, and lighter type ofantenna support thereof.

In another embodiment of the invention which is illustrated in Fig. 3,the structure of the antenna device is similar to that of the embodimentof Figs. 1 and 2 with the following exception. A solid wall member 48which has a tunnel-like configuration is utilized in lieu of the opencage-like structure disclosed in the preferred embodiment. The feeder 44is spaced from the bottom of the tunnel 48. The tunnel has a reflectorthat is mounted at one end thereof and the other end extendssubstantially beyond the feeder 44 and serves as the antenna aperture.The tunnel 48 is pivotably mounted by a yoke 20 and drive means similarto the preferred form. Likewise, the tunnel antenna device may becontinuously rotated and selectively tilted by said drive means.

The tunnel 48 and the supporting yoke structure are of a novel design.The skin of the tunnel 48 is the same as the surface of the antenna andthe hairflex is preferably laced to the tunnel surface 48 with nylonthread. The tunnel 48 can be made so that complete sections of thetunnel and the hairfiex can be fabricated elsewhere and joined togetherat the antenna site. The structure as shown is a truss type design whichprovides lightness and incorporated convenient points of dismantlementfor ease of transportation.

An experiemental investigation of side lobe reduction through the use ofspecific tunnel techniques indicates that a 40 db to 50 db reduction ispossible in the 60 to 180region with only slight loss in gain and slightincrease in beam width at the lesser tunnel depths. In the extremetunnel depths a reduction of the near side lobes is possible but anadded loss in gain appears at these depths and tunnel configurations.

The above described tunnel construction has been found to reduceconsiderably secondary lobe formation, for example, to such an extent asto improve greatly the operation of aircraft landing systems embodyingthe same.

Thus, the invention, as illustrated in Figure 3, comprises obtaining areduction of objectionable side lobes in the radiation pattern bythepredetermined construction of the tunnel.

Although the invention has been described with reference to thetransmission of radio energy it will be apparent to those skilled in theart that the constructions described herein may also be used forreception of other energy.

Further, while there has been here described what is at presentconsidered two embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention.

What is claimed is:

1. In a radar antenna device, a compact balanced antenna unit comprisinga paraboloidal reflector having a plane of symmetry which substantiallyincludes the axis of the radiation pattern therefrom, a feeder means forfurnishing thereto electromagnetic wave energy having a polarizationaxis parallel both to said reflector and to said symmetrical plane, saidfeeder means being located in a plane parallel and contiguous to saidsymmetrical plane of said reflector to accommodate the passage of theradiated energy thereto, oval-shaped means for supporting said reflectorand said feeder means, said oval-shaped means having flat portions topermit the radiated energy to be distributed more readily from saidfeeder means to said reflector; a yoke member having a vertical shaftportion and upwardly outwardly curved bar portions for supporting saidoval-shaped means on the upper ends of said bar portions whereby saidantenna unit is maintained in a balanced condition; drive means engagingsaid oval-shaped means for selectively tilting said antenna unit to anydesired angle of elevation; and additional drive means engaging saidvertical shaft portion for rotating said antenna unit in azimuth.

2. In a radar antenna device, a compact balanced antenna unit comprisinga paraboloidal reflector having a plane of symmetry which substantiallyincludes the axis of the radiation pattern therefrom, a feeder means forfurnishing thereto electromagnetic wave energy having a polarizationaxis parallel both to said reflector and to said symmetrical plane, saidfeeder means being located in a plane parallel and contiguous to saidsymmetrical plane of said reflector to accommodate the passage of theradiated energy thereto, oval-shaped member for supporting saidreflector and said feeder means, said oval-shaped member having aplurality of supporting rods rigidly fastening said oval-shaped memberto the outer periphery of said reflector, said oval-shaped member havingflat portions to permit the radiated energy to be distributed morereadily from said feeder means to said reflector; a yoke member having avertical shaft portion and upwardly outwardly curved bar portions forsupporting said oval-shaped member on the upper ends of said barportions whereby said antenna unit is maintained in a balancedcondition; drive means engaging said oval-shaped member for selectivelytilting said antenna unit to any desired angle of elevation; andadditional drive means engaging said vertical shaft portion for rotatingsaid antenna unit in azimuth.

3. In a radar antenna device, a compact balanced antenna unit comprisinga paraboloidal reflector having a plane of symmetry which substantiallyincludes the axis of the radiation pattern therefrom, a feeder means forfurnishing thereto electromagnetic wave energy having a polarizationaxis parallel both to said reflector and to said symmetrical plane, saidfeeder means being located in a plane parallel and contiguous to saidsymmetrical plane of said reflector to accommodate the passage of theradiated energy thereto, a solid Wall oval-shaped member for supportingsaid reflector and said feeder means, said oval-shaped member havingflat portions to more readily permit the radiated energy to bedistributed from said feeder means to said reflector; a yoke memberhaving a vertical shaft portion and upwardly outwardly curved barportions for supporting said oval-shaped member on the upper ends ofsaid bar portions whereby said antenna unit is maintained in a balancedcondition; drive means engaging said oval-shaped member for selectivelytilting said antenna unit to any desired angle of elevation; andadditional drive means engaging said vertical shaft portion for rotatingsaid antenna unit in azimuth.

4. A radar antenna device comprising a stationary base, means includinga vertical shaft for rotating said antenna device in azimuth, a casingmounted on said base for housing said rotating means; a yoke memberincluding said vertical shaft and uprightly outwardly curved bars; anoval-shaped member pivotably mounted on the ends of said bars, saidoval-shaped member having a flat bottom portion; means mounted at one ofthe ends of said bar portions for moving said oval-shaped member to anydesired angle of elevation; at paraboloidal reflector; a plurality ofsupporting rods rigidly fastening said ovalshaped member to the outerperiphery of said reflector, several of said supporting rods are bentdownwardly to engage said flat bottom portion; a feeder means positionedat a lower level than said reflector for furnishing electromagnetic waveenergy to said reflector; a plurality of additional supporting rodsrigidly fastening said feeder means to said oval-shaped member, one ofsaid additional rods constituting a wave guide member; the structuralarrangement of said flat-bottomed oval-shaped member and of said bentsupporting rods allowing the radiated energy from said feeder means tobe distributed more readily over said paraboloidal reflector.

References Cited in the file of this patent UNITED STATES PATENTS2,530,098 Van Atta Nov. 14, 1950 2,554,119 Perham May 22, 1951 2,617,032Allison Nov. 4, 1952 2,719,921 Cairnes Oct. 4, 1955 2,842,767 DarrouzetJuly 8, 1958 2,877,459 Brown et a1 Mar. 10, 1959

